Because such statements deal with future events and are subject to many risks and uncertainties, actual results may differ materially from those projected in the forward-looking statements. Examples of such risks and uncertainties include whether Optimer and its partners will be able to drive further adoption in sales of DIFICID, including in new markets and territories, whether Optimer's lifecycle management initiatives will ultimately result in label expansion, risks involved in the regulatory approval process, and the uncertainty in forecasting future cash requirements and financial results.For a full disclosure of these risks and uncertainties, please review Optimer's annual report on Form 10-K and subsequent quarterly reports on Form 10-Q as filed with the U.S. Securities and Exchange Commission. Furthermore, this conference call contains time-sensitive information that is accurate only as of the date of the live broadcast, July 31, 2012. Optimer undertakes no obligation to revise or update any statements to reflect events or circumstances after the date of this conference call. This conference call is also being webcast and will be archived on our website for 30 days after today. Earlier today, we released financial results for the second quarter ended June 30, 2012. If you've not received this news release, or if you'd like to be added to the company's distribution list, please visit the Investor Section of our website at www.optimerpharma.com. I would now like to turn the call over to Pedro Lichtinger, Optimer's President and CEO. Pedro Lichtinger Thank you, David. July 18 mark the one year anniversary of the launch of DIFICID, and we're very proud of our accomplishments. From launch last year, to the end of June, we achieved $51.1 million in net sales and shipped almost 20,000 treatments. We surpassed our 12-month sales gross established with Cubist. And so, Cubist has earned a $5 million bonus payment and a portion of the gross margin above that threshold.
Clearly, we have exceeded expectations for the first year after launch. Looking more closely at the second quarter, demand for DIFICID continue to grow. Ex-factory gross sales grew from $16.4 million to $18 million, an increase of over 9%. Ex-wholesaler sales grew by 11%. Net sales grew by 6% as discounts expanded the gross to net from 12.6% to 15.2% as a result of new contracts with group purchasing organizations, expanded coverage from providers and the impact of the Medicare Part D coverage gap, commonly referred to as the donut hole. Given the success we are seeing across all payors channels where Optimer contract, especially Medicare Part D, where we not only contract with the actual payors but also incur liabilities related to the Medicare Part D doughnut hole, and institutional care settings where Optimer also make contract, such as long-term care. We expect that our projected gross to net will moderately -- will be moderately higher than the 15% range previously guided.Given that demand in this setting is continuing to mature, we're hesitant at this point to give a specific number. Ex-factory growth was affected by a quarter end decrease in inventory levels at the wholesalers, which led to a softer than expected June. This trend was the opposite of what happened in quarter 1 when ex-factory net sales grew by 21%, while ex-wholesalers sale grew by 19%. In the first 4 weeks of July, we experienced a growth of 13% in the average exposure of demand when compared to the June weekly average demand regaining momentum. I believe, we continue to make significant progress in executing an impactful launch. As one would expect, we have learned a lot about C. diff and how hospitals treat it. Our flexibility and nimbleness to rapidly adapt to the market, as well as DIFICID's profile and the need for a new and innovative medicine to combat C. diff will allow us to continue to help patients execute an impactful launch and build value for our shareholders. Read the rest of this transcript for free on seekingalpha.com